Automatic Packaging Machine

ABSTRACT

Automatic packaging machine, comprising a tubular forming element ( 1 ) into which the product ( 6 ) to be packaged is introduced and around which at least one layer of plastic film ( 2 ) for forming the packages ( 13 ) is wrapped; this machine comprises: forming means ( 7 ) for wrapping the film ( 2 ) around said tubular element ( 1 ) so that at least two strips ( 2′,2 ″) of said film are superimposed in the longitudinal direction (L); means ( 9, 91 ) for feeding said film ( 2 ) along said tubular element ( 1 ); at least one welding bar ( 11 ) able to perform a longitudinal weld of said superimposed strips of the film ( 2 ); said bar ( 11 ) is able to move at least in a transverse direction (T) towards or away from said tubular forming element ( 1 ); and movable units ( 14, 14′, 14″, 114 ) for transversely welding and cutting the film ( 2 ) in tubular form leaving said tubular forming element ( 1 ), said movable units ( 14, 14′, 14″, 114 ) being positioned downstream of said longitudinal welding bar ( 11 ) on at least two diametrically opposite sides of the film ( 2 ).

The present invention relates to a packaging machine.

As is known, packaging machines may be horizontal or vertical and manual or automatic in nature and are used in order to obtain finished packages of loose products. In automatic packaging machines a certain quantity of loose product is introduced inside a hollow tubular element which defines the shape of the packet to be obtained. A plastic film is wrapped around this tubular element in an extremely complex manner in the known machines and is drawn downwards and then undergoes longitudinal welding by welding means. The welding process performed by these welding means is inefficient and discontinuous since there are long pauses between one welding operation and the next. At the end of said longitudinal welding operation performed by means of these transverse welding means, the film which will form the product packaging must be welded in the transverse direction so as to close the top and bottom of the packages. In this case also, the transverse welding process of the known machines is complex and discontinuous.

The object of the present invention is therefore to provide an automatic packaging machine which overcomes the drawbacks of the known packaging machines and which makes the package production cycle more efficient and rapid, in particular ensuring in an advantageous manner practically continuous operations for longitudinally and transversely welding and transversely cutting the plastic film from which the packages containing the finished product are obtained.

This object is achieved by the present invention by means of an automatic packaging machine according to Claim 1.

Further advantageous features of the present machine form the subject of the dependent claims.

Further characteristic features and advantages of the present invention will be understood more clearly from the following description, to be regarded purely by way of a non-limiting example and with reference to the accompanying drawings in which:

FIG. 1 shows a side elevation view of a packaging machine according to the present invention, comprising a tubular forming element around which a plastic film for producing the packages is wrapped;

FIG. 2 shows a front view, on a larger scale, of part of the present machine;

FIG. 3 shows a side elevation and partially sectioned view of the machine showing a forming collar for the plastic film from which the packages are made and the longitudinal welding means;

FIG. 4 shows one of the two belts for drawing and feeding the plastic film wrapped around the tubular forming element according to FIG. 1;

FIG. 5 shows, on each side of the film, two units for transversely welding and cutting the packets, provided with associated driving means which form a closed annular path and electric power supply means;

FIG. 6 shows a plan view of the machine partially sectioned along the line VI-VI shown in FIG. 5;

FIG. 7 shows a front view of a variation of embodiment of the present machine comprising a system for folding the bottom of the packages, provided at the bottom end with two oppositely arranged folding members shown at the minimum distance from each other;

FIG. 8 shows a front view—similar to the view of FIG. 7—in which said folding members are situated at a maximum distance from each other;

FIG. 9 shows a side elevation and partially sectioned view of the present machine along the line IX-IX shown in FIG. 7;

FIG. 10 shows a plan view, on a larger scale, of the central part of FIG. 5 relating to the two transverse welding units facing each other and comprising a cutting blade and a counter-blade shown in the open position with the plastic film inserted between them;

FIG. 11 shows a view—similar to the view of FIG. 10—in which the cutting blade and the counter-blade have been extracted from the associated welding units in order to cut the plastic film and then separate the packages produced by the present machine;

FIGS. 12 a and 12 b show schematically the two positions shown in FIG. 10 and FIG. 11, respectively, of the cutting blade and counter-blade and separation of the packages;

FIG. 13 shows a side elevation view, on a larger scale, of the belts for feeding the plastic film, provided with an electric motor providing power and acting as a counterweight;

FIGS. 14 a, 14 b, 14 c, 14 d show plan views of the cam tracks for guiding the transverse welding and cutting units where these tracks are provided with an interchangeable section for forming packages of different length;

FIG. 15 shows a plan view of three units for transversely welding and cutting the packages, connected to drive means which form two closed annular paths of substantially triangular shape;

FIG. 16 shows a side elevation and partially sectioned view of a carousel for conveying and unloading the finished packages;

FIG. 17 shows a plan view of a variation of embodiment of the present machine, relating to two oppositely arranged units for transversely welding and cutting the packages;

FIG. 18 shows, on a scale larger than that of FIG. 17, the two units for transversely welding and cutting the packages;

FIG. 19 shows a side elevation view of the welding unit with associated supports according to FIG. 17;

FIG. 20 shows a side elevation and partially sectioned view of a dispenser for the loose material to be packaged, arranged upstream of the tubular forming element;

FIGS. 21 a and 21 b show two side elevation and sectioned views of a variation of embodiment of the tubular forming element containing two series of baffles for allowing the loose material to move down stepwise along said tubular forming element;

FIG. 22 shows a partial side elevation view of one of the two series of baffles according to FIGS. 21 a and 21 b;

FIG. 23 shows a front view of one of the two series of baffles according to FIGS. 21 a and 21 b; and

FIGS. 24 a and 24 b show one of the baffles in the retracted position and operating position, respectively.

With reference to the accompanying figures and with particular reference to FIG. 1 thereof, 1 denotes a tubular forming element which is internally hollow and around which a layer of plastic film 2 is wrapped, said film being removed from a spool 3 around which it has been initially wound. This spool 3 is idle and is able to rotate about a central pin 4. The tubular forming element 1 may have any shape depending on the shape of the packaging or packet of product which is to be obtained, and therefore may have a circular, square, rectangular, polygonal or similar profile. The top part of the tubular forming element 1 has an inlet mouth 5 for introducing into it the product 6 to be packaged. This inlet mouth 5 is shown as having underneath it a forming collar 7 which has the function of correctly wrapping the plastic film 2 around the tubular forming element 1. This forming collar 7 comprises a first rear inclined surface 107 and two front inclined surfaces 207 and will be described in detail with reference to FIG. 2 of the accompanying drawings. The film 2 in the form of a continuous sheet reaches the rear surface 107 of the forming collar 7 with the correct inclination via a transmission roller 8 situated between this forming collar 7 and the spool 3. The plastic film 2, when wrapped in its tubular form around the tubular forming element 1, is drawn downwards along the longitudinal axis L of the tubular forming element 1 by means of a pair of feed belts 9 and 9′ located in diametrically opposite positions with respect to the tubular forming element 1. Each of these belts 9 and 9′ is operated by a pair of rollers 10 and 10′, at least one of which is motor-driven. Each pair of rollers 10 and 10′ is aligned along an axis parallel to the longitudinal axis L of the tubular forming element 1. A first bar 11 for longitudinally welding said plastic film 2 in tubular form is provided upstream of the said pair of belts 9 and 9′ for feeding the plastic film 2 and the tubular forming element 1 houses internally a second reaction bar 12 for said first longitudinal welding bar 11. This longitudinal welding 11 bar may be displaced upwards or downwards along the longitudinal axis L of the tubular forming element 1, or transversely, in a direction T perpendicular to the longitudinal axis L, away from or towards the tubular forming element 1. The second bar 12 reacting against this first bar 11 moves only in the longitudinal direction L and simultaneously with said first bar 11. The tubular forming element 1 is provided downstream, on each side of the film 2 leaving said tubular forming element 1, with two units 14 and 14′ for transversely welding and cutting the packages obtained, one package 13 of which containing a given quantity of product 6 being shown in the figure. Each of these welding units 14 and 14′ is associated with driving means such as a pair of chains 15 and 15′ (see FIG. 6), belts or the like. These chains 15 and 15′ are each wound around a pair of toothed wheels 16, at least one of which is connected to operating means (not shown). The two welding units 14 and 14′ fastened to each pair of chains 15 and 15′ are located in diametrically opposite positions with respect to said chains 15 and 15′ which define, along the sides of the film 2—see, for example, the two chains 15 in FIG. 1—two closed and identical annular paths along which said welding units 14 and 14′ move.

The forming collar 7 and the tubular element 1 are fixed and fastened to a support structure 17—see FIG. 2 of the accompanying drawings. The support structure 17 also has, fastened thereto, a guide 18 along which a slide 19 for operating the longitudinal welding bar 11 is able to slide, said slide being fastened to a support frame 20 connected, via a cross-piece 21, to said slide 19. The longitudinal welding bar 11, as seen above, may also be displaced transversely and, for this purpose, an actuator (not shown in the figures) and a pair of transverse guides 22 are provided for operation thereof. This longitudinal welding bar 11 must always face and practically make contact, during the welding operation, with the reaction bar 12 shown in FIG. 1; therefore a suitably shaped longitudinal groove 101, inside which said reaction bar 12 is able to slide, is formed along the tubular forming element 1. This longitudinal groove 101 is closed towards the inside of the tubular forming element 1 so as to prevent the product 6 from coming out of this tubular forming element 1 and essentially forms a kind of suitably shaped longitudinal recess. The forming collar 7 comprises, as seen, the rear surface 107, visible in FIG. 1, which has an inclination such as to move the film 2 substantially towards the top of the tubular forming element 1, and therefore an upwards inclination, and the two front surfaces 207 and 207′, which are inclined in the opposite direction to said rear surface 107 and are spaced from each other substantially by an amount equal to the diameter of the tubular forming element 1. The forming collar 7 comprises, downstream of each of said front surfaces 207 and 207′, substantially triangular elements 307 and 307′ for superimposing the strips of the film 2 according to FIG. 1. These elements 307 and 307′ for superimposing the plastic film are arranged over each other and intersect along their end part, but are suitably spaced from each other so that a strip of said film is able to pass between them. The tubular forming element 1 and the forming collar 7 are also spaced from each other so that the film can be inserted between them: in this connection an annular cavity 23 of suitable width for introducing the film which will form the package 13 according to FIG. 1 is formed between said tubular forming element 1 and said forming collar 7. Basically the plastic film passes in the form of a sheet over the rear inclined surface 107 of the forming collar 7 and is then wound onto the two inclined surfaces 207 and 207′ so that two strips are formed and move towards each other, owing to the inclination of these surfaces 207 and 207′; then one strip passes over the superimposing element 307 and the other strip passes between this element 307 and the superimposing element 307′; finally, the strips thus superimposed are introduced into the annular cavity 23 in order to obtain a tubular plastic film, i.e. with a shape corresponding to that of the tubular forming element 1 and with two longitudinal strips superimposed and subsequently welded longitudinally by the movable longitudinal welding bar 11.

FIG. 3 shows a sectioned side view of the forming collar 7. As can be seen, the film 2 is introduced into the annular cavity 23 formed between the tubular forming element 1 and said forming collar 7. With reference to the figure, on the left-hand side of the tubular forming element 1 it is possible to note the two superimposed longitudinal strips of plastic film 2—denoted by 2′ and 2″—which are welded together by means of the longitudinal welding bar 11. This bar, as mentioned above, is displaced transversely forwards, when welding must be performed, or backwards, in order to move it away from the tubular element 1, by means of an actuator 24 provided with an associated piston 25. The transverse displacement of the longitudinal welding bar 11 is guided by the transverse guides 22 which slide inside associated through-holes 26 formed in the frame 20 supporting the welding bar 11. This support frame 20, by means of an arm 27, also supports the reaction bar 12, this arm 27 in fact being connected to said plate 12 by means of a longitudinal rod 28. Said reaction bar 12, as mentioned above, slides inside the longitudinal groove 101 and is positioned on the outer edge of said longitudinal groove 101 so as to face the welding bar 11 at a minimum distance therefrom. Owing to this support frame 20 which firmly supports both the bars 11 and 12, said bars 11 and 12 are able to move simultaneously in the longitudinal direction, upwards or downwards, and the film 2 to be welded is always positioned between them.

FIG. 4 shows one of the two belts for feeding the film 2 in the longitudinal direction and downwards, in this case the belt 9. Said belt 9 is rotationally driven by the pair of rollers 10 and 10′ and the film 2 which must be fed is positioned between the side of this belt 9 directed towards the tubular forming element 1 and a series of reaction rollers 29 which also make contact with the film and are designed to allow the belt to feed said film 2 forwards. These reaction rollers 29 are positioned inside a longitudinal groove 101′ formed in the tubular forming element 1 and are positioned substantially along the outer edge of this groove 101′ so as to come into contact with the film, without however interfering with its tubular extension around the tubular element 1. This longitudinal groove 101′ is situated diametrically opposite to the longitudinal groove 101 already illustrated in FIGS. 2 and 3. This longitudinal groove 101 is able to seat, as mentioned, the reaction bar 12 and the other reaction rollers for the other belt 9′ feeding the film 2. In this case the belt 9′ shown in FIG. 2 is aligned longitudinally with the welding bar 11 and the associated reaction bar 12 and therefore only two, diametrically opposite, longitudinal grooves 101 and 101′ are formed in the tubular element. If, for example, the welding bar 11 were to be positioned at 90° with respect to these diametrically opposite feed belts 9 and 9′, three longitudinal grooves would be formed on the tubular forming element; one for housing the reaction bar 12, one for the reaction rollers of the belt 9′ and one for the reaction rollers of the belt 9.

With reference to FIGS. 5 and 6 of the accompanying drawings the transverse welding units are described below, said units having the function of welding the top and bottom of the package 13 shown in FIG. 1 and at the same time separating the packages from each other during the packaging process. FIG. 6 shows the two welding units 14 and 14′ situated on the left of the film 2 in FIG. 5. Each of these welding units 14 or 14′ comprises at the free end a pair of welding teeth 30 which are hinged by means of pins 31 on a support piece 32 fastened to a plate 33; this plate 33 is connected, by means of a pair of arms 34 and a pair of associated spindles 35, to the pair of chains 15 and 15′ for driving the welding units 14 and 14′. Each of the two plates 33 is therefore movable together with the associated welding unit 14 or 14′. Each of these welding units 14 or 14′ also comprises a centring device so that, when two welding units are situated facing each other, their correct alignment thereof is ensured. This situation can be clearly seen in FIG. 5 where the two welding units 14 driven by the chains situated along the sides of the film 2 face each other and weld said film 2: the welding unit 14 situated on the left-hand side of the film 2 is in fact provided between the two welding teeth 30 with a notch 36, while the welding unit 14 situated on the right-hand side of the film 2 is provided between the two welding teeth 30 with a nose 37 having a shape matching that of said notch 36. Each of the two chains 15 and 15′, shown in FIG. 6, for driving the welding units 14 and 14′ is wound around the pair of longitudinally aligned toothed wheels 16 and 16′. The toothed wheels 16 and 16′ shown in FIG. 6 are keyed around a shaft 38 connected to transmission elements 39 in turn connected to a motor which essentially operates the shaft 38 which causes rotation of the toothed wheels 16 and 16′. In FIG. 6 the reference number 40 denotes a fixed structure which supports a pair of annular tracks 41 which are electrically energized. Each of the four welding units 14 and 14′ comprises at one end of the plate 33 an arm 42 for supporting a pair of carbon brushes 43 which make contact with the associated electrified track 41. This sliding electric contact formed between the carbon brushes 43 of the mobile welding units 14 and 14′ and the associated, fixed, electrified tracks 41 ensures that current is supplied continuously to the four welding units 14 and 14′. The end of each of the plates 33, opposite to that where the arm 42 is positioned, is provided, for each of the four units 14 and 14′, with another arm 44 supporting a pair of metal heads 45 each designed to slide on a metal annular track 46 positioned on the fixed structure 40 on the opposite side to that where the electrified tracks 41 are positioned. These sliding metal heads 45 transmit heat to sensor means, not shown, connected to a control unit which controls switching on and off of the power supply so as to keep the temperature of the welding systems substantially constant. The chains 15 and 15′, as mentioned above, drive during their movement along a closed annular path, the two welding units 14 and 14′ which also comprise support means which guide them correctly during this closed annular movement. Said support means comprise a fixed-cam track 47 along which a pair of idle rollers 48 travel for each welding unit 14 and 14′. These rollers 48 are mounted on a plate 49 which is connected to the associated arm 34 so that it is able to pivot relative thereto. The central part of FIG. 6 shows a second cam track 50 for controlling the cutting means—described below—which equip the welding units 14 and 14′. Idle rollers 51 mounted on the moving heads 52 equipping the welding units 14 and 14′ engage inside said cam track 50. As can be noted from FIG. 5, the two welding units 14 and 14′ of each of the two welding systems are connected to the two drive chains 15 and 15′ in diametrically opposite positions with respect to the closed annular path along which they must travel and which comprises: a first straight working section along which two units, for example the two units 14, face each other and make contact with each other, a first section in the form of a connecting circle-arc, a second straight return section along which the other two units—in this case the two units 14′, which are again situated in diametrically opposite positions and at a maximum distance from each other—are located, and a second annular connecting section.

By means of the units 14 and 14′ for transversely welding and cutting the packages described above it is therefore possible to obtain finished packages with a certain quantity of product inside. FIG. 7 shows a part of the present machine provided with a number of variants compared to that described hitherto. The tubular forming element 1 has, positioned internally, instead of the reaction bar 12 of the longitudinal welding bar 11 shown in FIG. 1, a movable tubular member 53 which is coaxial with the tubular forming element 1 and has a shape corresponding to its shape. This tubular member 53 acts as a reaction member for the longitudinal welding bar 11 and the product is therefore poured inside it. A longitudinal groove 201, which can be seen in FIG. 9, is therefore formed in the tubular forming element 1, in order to allow co-operation between the tubular member 53 and the longitudinal welding bar 11. The plastic film 2 is in this case also wrapped around the tubular forming element 1 and the machine likewise is provided with the forming collar 7 shown in FIG. 1. This tubular member 53 is fixed to a movable bar 54 which supports a slotted link 65 integral therewith. This bar 54 is able to move along fixed guides 55 which are integral with a support structure 60 to which the stationary tubular forming element 1 is also fixed. Said bar 54, in the figure, is shown in the fully lowered position along the guides 55. These guides 55 are formed along the sides of a central plate 56. Said plate 56 is passed through by a motor-driven shaft 57 which has a disc 59 fixed to its end and on which a first toothed wheel 58 is keyed. This disc 59 is provided on its periphery with an eccentric pin inserted inside the slotted link 65. A twin-lobe cam 61 is also connected to the movable bar 54 and has, connected thereto, a second toothed wheel 62. A chain 63 for transmitting the movement from the motor-driven shaft 57 to the disc 59 and ultimately to the cam 61 is wound around these first and second toothed wheels 58 and 62. In a middle zone this drive chain 63 is also wound around a transversely displaceable roller 66 able to ensure that the chain is always correctly tensioned. Two pins 67 are fixed to each end of said movable bar 54, for example the right-hand end when viewing the figure, each of these pins having, mounted thereon, the end of an arm 68, the other end of which is mounted on another pin 69 fixed onto a plate 70 to which a first folding member 71 is connected, said folding member projecting towards the tubular forming element 1 to a point close to the longitudinal axis of symmetry L thereof and being able to be displaced transversely with respect to this axis L from a minimum distance, shown in the figure, to a maximum distance from this axis L shown in FIG. 8. The two arms 68 are able to pivot about the associated pins 67 and 69 following, as will be seen below, the movement of the cam 61, forming with the movable bar 54 and with the plate 70 supporting the folding member 71 a kind of hinged parallelogram so that basically the folding member 71 performs an arc-like movement upwards or downwards, while remaining, however, always in a horizontal or transverse position with respect to the longitudinal axis L. Further two pins 67′ are similarly fixed to the left-hand end, when viewing the figure, of the movable bar 54, said pins having mounted thereon, in a manner identical to that described above, the ends of two arms 68′ which are connected at the other end to pins 69′ fixed to a plate 70 to which a folding member 71′ is connected, said folding member being identical to the folding member 71 and symmetrical with the latter relative to the longitudinal axis L of symmetry of the tubular forming element 1 and therefore of the packaging which is to be obtained from the film 2 wrapped around said tubular forming element 1. The twin-lobe cam 61 co-operates with two idle rollers 72 and 72′ which are located in diametrically opposite positions with respect to this cam 61 and mounted on an associated support rod 73 and 73′: these rods 73 and 73′ are fixed, respectively, to the arms 68 and 68′ directed towards the tubular forming element 1. The folding members 71 and 71′ have the function of folding two diametrically opposite sides of the bottom of the package to be formed by means of the plastic film 2.

FIG. 9, which is a side view of FIG. 7 described above, shows the kinematic chain which allows operation of the various moving parts described in FIG. 7. 74 denotes a motor for operating, via a series of transmission and reduction members, the shaft 57 on which the toothed wheel 58 is keyed and which has, fixed to its end, the disc 59 provided with the eccentric pin 64 inserted inside the slotted link 65 mounted on the movable bar 54. The following are therefore connected to the bar 54 displaceable vertically along the guides 56: the tubular member 53 inside the fixed tubular forming element 1, via a plate 76 for connecting said tubular member 53 to said bar 54; the twin-lobe cam 61 which, by means of a support 77 provided with associated bearing, is connected to a rod 78 connected to said movable bar 54; the folding members, of which the folding member 71 shown in FIG. 7 can be seen in the figure, with the associated arm 68 connected via the pivot pins 67 and 69 to the plate 70 and to the bar 54; and the longitudinal welding bar 11—already illustrated in FIG. 1—which co-operates by means of the longitudinal groove 201 with the tubular reaction member 53 and is displaced transversely by an actuator 24. This longitudinal welding bar 11 is connected to the plate 76 by means of an associated rod 20′ of the frame 20, so that said welding bar 11 and said tubular reaction member 53 move simultaneously in the longitudinal direction when the movable bar 54 is displaced along the guides 55.

FIG. 8 shows the situation where the members 71 and 71′ for folding the bottom of the packages are at the maximum distance from the longitudinal axis L of the tubular forming element 1 and therefore the plastic film. In this situation the eccentric pin 64 is rotated through 180° with respect to the position shown in FIG. 7, owing to rotation of the disc 59 moved by the motor 74. Said rotation of the eccentric pin 64 causes raising of the movable bar 54, by means of the slotted link 65 which is integral with the movable bar and engaged by said eccentric pin 64, and therefore raising of the tubular reaction member 53 which slides inside the tubular forming element 1. The toothed wheel 58 is also keyed onto the drive shaft 57 and, by means of the drive chain 63, causes rotation of the twin-lobe cam 61, in this case through 90°, so as to pass from the position shown in FIG. 7 into the position shown in FIG. 8. The simultaneous raising movement of the bar 54 and rotational movement of the cam 61 produce a pivoting movement and upwards displacement of the pairs of arms 68 and 68′ which are provided with the rods 73 and 73′ with the associated rollers 72 and 72′ which travel along the cam 61. Owing to the fact that each pair of arms 68 and 68′ is fastened to the bar 54 and to the associated plate 70 and 70′, so as to form a kind of hinged parallelogram, the bending members 71 and 71′ connected to the plates 70 and 70′ basically, in order to pass from the situation shown in FIG. 7 to the situation shown in FIG. 8, are raised and moved away, but always remains in a horizontal or transverse position with respect to the longitudinal axis L of the tubular forming element 1 and therefore the film. In order to ensure correct tensioning of the drive chain 63, the transmission roller 66 is displaced outwards and therefore away from the tubular forming element 1 from the situation shown in FIG. 7 into the situation shown in FIG. 8. It is also possible to understand clearly how, from the situation shown in FIG. 8, it is possible to pass again into the situation shown in FIG. 7 owing to a renewed rotational movement through 180° of the eccentric pin 64, lowering of the movable bar 54 and renewed rotation through 90° of the twin-lobe cam 61. These members 71 and 71′ for folding the bottom of the packages are positioned upstream of the transverse welding and cutting units 14 and 14′ shown in FIG. 1, FIG. 5 and FIG. 6.

FIG. 10 shows the two welding units 14 facing each other and designed to perform the welding operation, i.e. the units between which the film 2 in FIG. 5 is positioned. Each of these transverse welding units 14 comprises a box-shaped body 79 and 79′ containing, in addition to the welding means, also the film cutting means. In this case a cutting blade 80′ is located inside the box-shaped body 79′ of the welding unit 14 situated higher up when viewing the figure, while a counter-blade 80 with a receiving surface having a shape corresponding to the profile of the blade 80′ is positioned inside the box-shaped body 79 of the unit 14 situated lower down. Clearly the blade and the counter-blade could also be inverted, i.e. the blade 80′ could be positioned inside the box-shaped body 79 of the unit 14 situated at the bottom and the counter-blade 80 could be positioned inside the box-shaped body 79′ of the welding unit 14 situated at the top. The blade and the counter-blade 80′ and 80 are both supported by an associated tubular member 81 passing through a through-hole 82 formed in the plate 33—shown in FIG. 6—and associated with the chains 15 and 15′. A spindle 83 for guiding the blade 80′ and the counter-blade 80 is also fixed to this plate 33 and is able to slide inside an associated through-hole 84 formed inside the head 52 shown in FIG. 6. The box-shaped bodies 79′ and 79 are also connected to the plate 33 by means of support elements 85 arranged on the sides of the tubular member 81. The two units 14 are electrically powered by means of electrical connectors 86. As mentioned above, 50 denotes two cam tracks for controlling the cutting blade 80′ and counter-blade 80, inside which the idle rollers 51 connected to the heads 52 travel. This blade 80′ and counter-blade 80 may therefore move in opposite directions transverse to the film 2 owing to the translatory movement of the associated heads 52 and therefore the translatory movement of the tubular members 81 inside the associated through-holes 82 formed in the two plates 33. FIG. 10 shows the blade 80′ and the counter-blade 80 at the maximum distance from each other, while FIG. 11 shows the same blade and counter-blade engaged with each other, in order to cut the film 2: as can be noted by comparing FIGS. 10 and 11, the two heads 52 have moved towards each other performing a transverse translatory movement and are guided during this movement by the sliding movement of the spindles 83 inside the through-holes 84 and by the sliding movement of the tubular members 81 inside the through-holes 82.

The situations shown in FIG. 10 and in FIG. 11, respectively, are also schematically shown in FIGS. 12 a and 12 b, respectively: in FIG. 12 a it can be seen that the cutting blade 80′ is aligned transversely with respect to the counter-blade 80, but is spaced from it; while in FIG. 12 b it can be seen that this blade 80′ is engaged with the corresponding counter-blade 80. The cam tracks 50 inside which the rollers 51 guiding the blade and counter-blade support heads each have, in the cutting zone, i.e. the zone where the blade 80′ must engage with the counter-blade 80, a section 50′ inset towards the film 2 to be cut so as to allow the blade and the counter-blade to move towards each other, and therefore the cam tracks 50 along this section 50′ are closer to each other.

FIG. 13 shows the two belts 9 and 9′ for feeding the film 2 which assumes a tubular configuration with a shape corresponding to that of the tubular forming element 1 around which it is wrapped. These belts 9 and 9′ are moved by means of a motor 87 which operates a drive shaft 88 on which one of the two rollers of the belt 9′, in this case the roller 10′, and a first toothed wheel 89 are keyed. A drive belt or chain 90 is wound around said toothed wheel 89 and passes around a second toothed wheel 91 keyed onto the shaft 92 for supporting and rotating the roller 10′ of the belt 9. Said chain is then wound around a pair of toothed transmission wheels 93. The belts 9 and 9′ are mounted on associated plates 94 and 94′ which perform slight pivoting movements about the shafts 92 and 88, respectively. These plates 94 and 94′ are in turn mounted on a pivoting structure 95 which is pivotably hinged on a fixed structure (not shown) by means of a pin 96. The plates 94 and 94′ supporting the belts 9 and 9′ comprise, at the top, arms 97 and 97′, respectively, to which a rod 99 for connecting said plates 94 and 94′ is connected by means of a pair of pivot pins 98 and 98′. The film feeding belts 9 and 9′ are operated so that they move in the direction of the arrows T and T′ and always remain with their inner side in contact with the film 2 to be fed longitudinally downwards. The pivoting rod 99 combined with the pivoting structure 95 in fact ensure that these belts 9 and 9′ are always aligned with the tubular forming element 1 and therefore with the film 2. Moreover these belts 9 and 9′ may adapt to any width or diameter of the tubular forming element 1; in fact if we imagine a tubular forming element 1 with a width or diameter greater than that shown in the figure, the belt 9 would be situated lower down than in the situation shown and always in contact with the film 2, while the belt 9′ would be situated higher up than that shown and likewise always in contact with the film 2. This adaptation in the position of the belts 9 and 9′ is made possible by the motor 87 which also has the function of a counterweight (therefore, if the belt 9 were lowered and the belt 9′ raised, the motor 87 would also be raised) and by the fact that the structure 95 pivots with respect to the pin 96 (the plates 94 and 94′ may pivot with respect to the shafts 92 and 88, and the rod 99 connecting the plates in turn may pivot about the pins 98 and 98′). The correct definition of the weight of the motor 87 ensures the correct pressure of the belts 9 and 9; which must feed the film 2 downwards along the tubular forming element 1.

FIG. 14 a shows one of the cam tracks 47 with one of the two welding units 14 shown in FIG. 6. The rollers 48 are supported by the pivoting plate 49 which is connected to the associated arm 34 and therefore to the plate 33 by means of a pivot pin 100. The actual welder, not shown in the figure, is positioned on the side of the plate 33. This plate 49 pivoting about the pin 100 allows the formation of cam tracks also having bends with small radii of curvature, since the rollers 48 adapt to these bends. The cam track 47 has, in the case of all four situations shown in FIGS. 14 a-d, a working track section 147 a-d, i.e. a section along which two welding units 14 or 14′ are facing each other and performing the transverse welding operation, as shown in FIG. 5 for example. Each of these working sections 147 a-d has at its ends pins 102 for fixing to the remainder of the cam track 47 and therefore these working sections 147 a-d are interchangeable. The working section 147 a shown in FIG. 14 a is straight so that the active welding section coincides with said working section and is denoted by A1. The working section 147 b shown in FIG. 14 b instead has an inset portion 247 b where the units 14 or 14′ are spaced from each other and therefore welding does not take place, the active welding section therefore essentially being represented by the segment A2. In the situation shown in FIG. 14 c the active section A3 is shorter than the section A2 since the inset portion 247 c has a greater length, while in FIG. 14 d the active section A4 has an even smaller length, with an inset portion 247 d of the cam track 47 having a greater length than in the preceding cases. If it is assumed that, in each of the situations shown in FIGS. 14 a-d, the welding units with the associated plates 33 travel along the cam tracks at the same speed, the sections A1-A4 represent the time taken to perform transverse welding of the bottom of the packages; in other words, the shorter the welding time, and therefore the length of the working section A1-A4, the smaller is the length of the bags which are to be obtained using the present machine. In this case, if the cam track 47 is provided with a working section without inset portions, as shown in FIG. 14 a, a package with a greater length will be obtained than if working sections such as those shown in the following FIGS. 14 b-d are used; instead, if a working section comprising an inset portion 247 d as shown in FIG. 14 d is used, packages with a smaller length than in all the other cases shown in FIGS. 14 a-c will be obtained.

FIG. 15 shows another variant of the present machine where there are three pairs of transverse welding units which engage with each other in order to weld the film 2, i.e.: a first pair of welding units 14, a second pair of units 14′ and a third pair of welding units 14″. Three welding units 14, 14′ and 14″ are therefore provided for each kinematic chain situated along the sides of the film 2 to be welded. The situation is similar to that shown in FIG. 5 where two welding units 14 and 14′ are provided on each drive chain 15. In this case, each of the welding units 14, 14′ and 14″ travels along a triangular close-loop path so that the drive chains 15 are wound around three toothed wheels 16 arranged at the same distance from each other. The welding units 14, 14′ and 14″ are positioned halfway along the chain sections situated between one toothed wheel and the next one so that they are also spaced at the same distance from each other. The electrified tracks 41 on which the carbon brushes 43 slide will also have a triangular shape, as will the cam tracks 47 guiding the welding units 14, 14′ and 14″, said tracks 47 following a path situated on the outside of the drive chains 15 and the toothed wheels 16.

FIG. 16 shows a device for selecting and unloading the finished package from the present machine. 103 denotes a fixed base, for example in the form of a disc, comprising along its periphery a mouth 104 for unloading the finished packages 13. This fixed disc 103 has in the centre a through-hole 105 which receives a shaft 106 rotated by associated operating means (not shown). A rotating disc 107 is connected to said shaft and provided with a series of compartments 108 for receiving the finished packages 13 after the machine has filled each of them with the associated product and welded the top and bottom thereof. These packages, as a result of the disc 107, follow a given arc-like path relative to the fixed disc 103 until they reach the unloading mouth 104, where a conveyor belt for example, or the like, may be provided downstream, situated underneath said mouth.

With reference to all figures shown, operation of the present packaging machine will now be described below. During a first machine preparation stage, the plastic film 2 must be manually positioned around the tubular forming element 1 as far as the zone close to the feed belts 9 and 9′ which initially will be arranged at a suitable distance from said tubular forming element 1. The operator wraps the film 2 around the rear surface 107 and then around the front surfaces 207 and 207′ of the forming collar 7 and then inserts it into the annular cavity 23: a strip of film 2 will be positioned above the triangular element 307 and the other strip will be positioned between the two superimposing triangular elements 307 and 307′. At this point the film 2 assumes a tubular shape with two superimposed longitudinal strips 2′ and 2″ corresponding to the shape of the tubular forming element 1, and is displaced, again manually, as far as the zone of the feed belts 9 and 9′. Owing to a rotation about the pin 96 of the associated support structure 95, these belts 9 and 9′ are positioned so as to make contact correctly against the film 2 arranged around the tubular forming element 1. Contact between the said belts 9 and 9′ and the film 2 and tubular forming element 1 is ensured by the motor 87 which also has the function of a counterweight. The belts 9 and 9′, as mentioned above, may thus adapt to any width or diameter of the tubular forming element 1. At this point the motor 87 is activated and the rollers 9 and 9′ start to feed the film 2 downwards in a tubular form. During the downwards feeding of the film 2 the longitudinal welding bar 11 is displaced downwards, together with the reaction bar 12 or tubular member 53, and longitudinally welds the two superimposed strips of film 2. This bar 11 is operated by the means and mechanisms shown in FIG. 9. Said bar 11 must move longitudinally downwards at a speed greater than that of the film 2 to be welded and, once a section of film 2 has been welded, will be displaced transversely so as to move away from the tubular forming element 1, while the reaction bar 12 or the tubular member 53 remain stationary. The bar 11 and the bar 12 or the tubular reaction member 53 are displaced longitudinally upwards and therefore the bar 11 will be displaced again transversely towards the tubular forming element 1 in order to form a new longitudinal weld. Since said longitudinal welding of the two superimposed strips 2′ and 2″ of the film 2 must be performed continuously, the movements of the film 2 along the tubular forming element 1 and the cyclical movement of the bar 11 must be suitably synchronised. When the film 2 reaches the end of the tubular forming element 1 and protrudes from it by a suitable distance, first transverse welding units, for example the two units 14, perform initial welding of the bottom of the first package, while a suitable quantity of product has been introduced via the inlet mouth of the tubular forming element 1. Once this first welding operation has been completed, considering for example the configuration where there are two units 14 and 14′ for each conveying chain 15 as shown in FIGS. 1 and 5, these first two units 14 which have performed welding must be replaced by the second two units 14′ which are situated at the maximum distance from each other and from the film 2. Clearly the drive chains 15 and 15′ which form the annular paths situated along the sides of the film 2 move at the same speed. During the time which it takes for the second two welding units 14′ to reach the operating position, i.e. where they face each other, the package containing the product and welded along the bottom passes in between the closed-loop conveying chains 15 and 15′ and, therefore, when these second welding units 14′ are facing and aligned with each other, welding of the top of the package is performed, as can be seen in FIG. 1, for the first package 13. Said top of the first package 13 forms the bottom of the next package to be formed. Once welding has been completed the cutting blade 80′ and counter-blade 80 are extracted from said second two welding units 14′ so as to thus obtain the finished package which is allowed to fall into one of the compartments 108 of the rotating disc 107. The cycle for production of the packages therefore takes place continuously and without interruptions, also in the case of the configuration comprising three welding units 14, 14′ and 14″ shown in FIG. 15, since advantageously both the longitudinal welding bar 11 and the transverse welding units 14, 14′ and 14″, owing to the conveying chains 15 and 15′, move along closed-loop paths. As seen above, prior to welding of the bottom of the packages, the present machine may be provided with folding members 71 and 71′ which, via the motor 74 operating the bar 54 according to FIGS. 7 and 8 and the hinged arms 68 and 68′, move simultaneously and transversely towards or away from the tubular forming member 1 and therefore the film 2 in tubular form. These folding members 71 and 71′ have the function of folding two diametrically opposite strips of the film 2 which will form the package, and each of them is positioned at about 90° with respect to the transverse welding units 14 and 14′ which are arranged downstream of said folding members. The movement of these folding members 71 and 71′ is also continuous owing to the rollers 72 and 72′ which travel on the twin-lobe cam 61 and rotation of the latter, so that the movement of these folding members must also be synchronized with the remainder of the moving parts of the present machine.

Below a variant of the present machine will be described where the longitudinal welding bar 11 performs a backwards and forwards transverse movement in the direction T relative to the tubular forming element 1 and therefore the film 2. This movement is made possible by a linear actuator 150 schematically shown in FIG. 1. This longitudinal welding bar 11 in this case welds the package at the same time as the two opposite welding and cutting units 114 shown in FIGS. 17, 18 and 19. The movements of said bar 11 and said units 114 will obviously be synchronized. With reference to said FIGS. 17, 18 and 19, each of the said units 114 for transversely welding and cutting the packages comprises a pair of welding heads 151. A cutting blade 80′ is inserted between the two heads 151 of the welding and cutting unit 114 situated on the right-hand side when viewing FIGS. 17 and 18, while a counter-blade 80 is inserted between the two heads 151 of the unit 114 situated on the left-hand side. Each of the two units 114 is connected to a linear actuator 152 provided with an associated support 153 and able to move transversely backwards and forwards, and therefore towards or away from the double film 2, the associated unit 114 for transversely welding and cutting the packages. Each of the units 114—see for example the unit equipped with the blade 80′ shown in FIG. 19—passes through an opening 154 formed in a cross-piece 155. As can be seen also in FIG. 18, the two cross-pieces 155, through which the two units 114 will pass during welding and cutting, face each other and the double film 2 is clamped in position between them. Each of the cross-pieces 155 is supported at each end by a support plate 156, see for example FIG. 19 where it can be seen that each cross-piece is provided with two support plates 156 connected to the ends thereof. Each of the plates 156 is provided with a pair of pins 157 by means of which it is connected to an associated drive chain 158 which performs a substantially triangular movement around three toothed wheels 159 arranged at the same distance from each other. The structure housing the two welding units 114 comprises two parallel side walls 160 connected together by means of cross-pieces 161. Two symmetrically arranged tracks 162 with a substantially triangular shape are fixed to each of said side walls 160—compare FIGS. 17 and 19 in this connection. The plates 156 supporting the cross-pieces 154 move along these triangular tracks 162 by means of two pairs of rollers 163 which travel idle and in contact with either side of said track. Each pair of said rollers 163 is fastened to a plate 164 which is free to pivot, so as to follow the bends along the triangular path of the track 162, about a central pin 165 integral with the plate 156. The four drive chains 158 are positioned along the associated track 162 and, in each pair of chains provided on each side wall 160, these chains 158 are also symmetrically arranged with respect to each other, as can be seen in FIG. 17. These chains are operated by means of a motor 166 which causes rotation of an associated shaft 167 which passes through the structure from one side wall to the other and which has, keyed thereon, the first of a pair of identical and counter-rotating gear wheels 168. Basically the drive shaft 167 causes rotation of the two gear wheels 168, and the two shafts on which they are keyed, i.e. said drive shaft 167 and the driven shaft 167″, pass through the structure from one side wall to the other one, thereby essentially ensuring the synchronous movement of the four chains 158. 167′ denotes the other driven shafts of the other toothed wheels, shown at the bottom in FIG. 17. Obviously, in each pair of symmetrically arranged chains 158 driving the plates 156, a given chain moves in the opposite direction to the other chain. As can be seen in FIG. 17, each section of each track of the pair of symmetrically arranged tracks 162 is provided with a plate 156 supporting an associated cross-piece 155 provided with the opening 154. Basically, therefore, the structure will be provided with three pairs of cross-pieces 155, each of said cross-pieces being supported by a pair of plates 156. These cross-pieces 155 come into contact with the double film along the upper toothed wheels 159 shown in FIG. 17 and remain in contact therewith until they reach the zone close to the two lower toothed wheels 159. As can be understood, owing to the triangular tracks, the double film 2 for forming the packages is therefore practically always in contact with a pair of cross-pieces 155 which rotate on the triangular tracks 162, ensuring an advantageous continuity during the packaging operations.

As mentioned above, the longitudinal welding bar 11 and the two transverse welding and cutting units 114 operate together in this variant of the present machine. Considering the situation shown in FIG. 17, when two of the cross-pieces 155 are in position and clamp the double film 2, the bar 11 is displaced towards the tubular forming element 1—see FIG. 1—by means of the actuator 150 and performs longitudinal welding of two superimposed strips of the film 2. At the same time, the two units 114 are displaced, by means of two actuators 152, towards the double film 2 passing through the associated openings 154 formed in the two cross-pieces 155. These units are each provided with a double welding head 151 so that the heads 151 situated at the top in FIGS. 17, 18 and 19 will weld the two strips of the bottom of a package situated upstream, while the two heads situated at the bottom will weld the two strips of the top of a package situated downstream. At the same time, the blade 80′, cooperating with the associated counter-blade 80, will separate these two packages situated upstream and downstream. The simultaneous longitudinal welding, transverse welding and cutting operations for separating the packages require a very short interruption in the machine cycle, which interruption may be defined as having a duration of about 1/10 of a second, so that the process implemented by the present machine is practically continuous also in this variant just described.

FIG. 20 shows a dispenser 169 for dispensing loose material to be introduced into the inlet opening 5 of the tubular forming element. This loose material will be packaged in the manner described above. The dispenser 169 comprises a central metering unit 171 which is divided into two chambers 172 and 172′ into which a certain quantity of loose material 173 may be introduced via a top inlet mouth 170. By way of example the figure shows the chamber 172 filled with loose material 173. These chambers are closed at the bottom and at the top by movable hatches: the chamber 172 is closed at the top by the hatch 177 a and at the bottom by the hatch 177 b, while the chamber 172′ is closed at the top by the hatch 178 a and at the bottom by the hatch 178 b. This central unit 171 is supported on two opposite sides by suitable fixed supports 174, while each of the hatches 177 a, 177 b, 178 a and 178 b is displaced in one direction or the other by means of an associated linear actuator 179. The device 169 comprises downstream of the unit 171 a bottom wall 175 provided with an opening 176 for allowing the loose material 172 to pass from this unit 171 into the inlet mouth 5 of the tubular forming element.

Basically the dispenser 169 ensures that a certain quantity of product always reaches the tubular forming element in an efficient and rapid manner, thereby speeding up greatly the operating process of the present machine. Considering the situation shown in FIG. 20, the material 173 has been introduced into the chamber 172 through the top opening thereof left open by the hatch 177 a in the retracted position. The bottom hatch 177 b is instead closed. The hatches 178 a and 178 b of the other chamber 172′ are in precisely the opposite position, namely the top hatch 178 a is closed while the bottom hatch 178 b is open. When the hatch 177 a of the chamber 172 is opened, the material passes by means of gravity into the inlet opening 5: at the same time the hatches 177 a and 178 b are closed and the hatch 178 a is opened, allowing a certain quantity of other loose material to be poured into the other chamber 172′. The process is repeated with the loose material which ultimately reaches the inlet opening 5 alternately via the chamber 172 and the chamber 172′ and when one chamber is emptied simultaneously the other chamber is filled.

FIG. 20 shows two oppositely arranged series of three movable baffles 182 a-c and 183 a-c. These baffles, which may also consist of a number greater or smaller than that shown, are arranged suitably spaced from each other and have the function of forming alternating steps along the inner channel 180 of the tubular forming element 1 through which the loose material 173 passes. These baffles basically have the function of preventing the loose material to be packaged from falling by means of gravity from the top to the bottom of the tubular forming element all in one go. Such a falling action could in fact be harmful and damage the loose material in the case where it is not of solid or resistant nature. As can be seen, the baffles of one series are alternated with the baffles of another series, and therefore the sequence of baffles, starting from the top of the tubular forming element, is as follows: 182 a, 183 a, 182 b, 183 b, 182 c and 183 c. The movable baffles of each series are connected to a connection plate 184 and are displaced upwards or downwards by means of an associated actuator 185. Each of these baffles may be made of plastic or metal and must possess a certain flexibility and elasticity so that they can be suitably bent. Two chambers 181 and 181′ for respectively housing said two series of oppositely arranged baffles 182 a-c and 183 a-c are formed on the outside of two oppositely arranged walls 186 of the central channel 180 through which the loose material 173 passes. Each of these oppositely arranged walls 186 are provided with holes 187 through which each of said baffles can protrude from the associated chamber 181 and 181′. As can be seen, the chambers 181 and 181′ are at least open at the top so as to allow the baffles 182 a-c and 183 a-c to protrude from the top and be operated by means of the associated actuators 185.

Fixed pins 188 are positioned inside each of the chambers—see for example the chamber 181 in FIG. 22—and engage with the baffles along the eyelets 189 formed therein—see in this connection the front view of FIG. 23 showing the three baffles 182 a-c. The length of these eyelets essentially defines the upward or downward travel of each of the three baffles which move simultaneously.

Each of these baffles—see for example the baffle 182 a shown in FIGS. 24 a and 24 b—is guided during its movements into and out of the central channel 180 by two curved grooves formed in two opposite walls of said central channel. These figures show one of the said grooves, i.e. the grooves 190 formed in the wall 186 of the central channel 180.

The operating principle of these baffles can be easily understood. In FIG. 21 a the three baffles 182 a-c are in the lowered position, i.e. are completely extracted from the holes 187 of the chamber 181 and therefore form steps for the loose material 173 supplied from the inlet mouth 5. This material therefore falls onto the first baffle 182 a. The baffles of the other series 183 a-c are instead in the retracted position and completely raised. At this point the baffles 182 a-c are raised and retracted and, as a result of their elasticity, assume the position shown in FIG. 21 b, while the baffles 183 a-c are lowered and inserted into the channel 180. Said insertion is performed by means of elastic deformation of the said baffles which are guided by the grooves 190 mentioned above and/or moreover are inserted inside a slit 192 formed in the wall 186 opposite to that in which the outlet holes 187 are formed. The loose material 173 then passes from the first baffle 182 a, which has been retracted, to the first baffle 183 a, gradually moving stepwise towards the bottom of the tubular forming element 1. At this point the baffles 183 a-c are retracted and raised, while the baffles 182 a-c are again extracted and lowered and the loose material passes from the baffle 183 a to the baffle 182 b. This operation will continue to take place until the loose material has reached the bottom of the tubular forming element ready for packaging. 

1. Automatic packaging machine, comprising a tubular forming element into which the product to be packaged is introduced and around which at least one layer of plastic film for forming the packages is wrapped, characterized in that it comprises: forming means for wrapping the film around said tubular element so that at least two strips of said film are superimposed in the longitudinal direction; means for feeding said film along said tubular element; at least one welding bar able to perform a longitudinal weld of said superimposed strips of the film, said bar being able to move at least in a transverse direction towards or away from said tubular forming element; and movable units for transversely welding and cutting the film in tubular form leaving said tubular forming element, said movable units being positioned downstream of said longitudinal welding bar on at least two diametrically opposite sides of the film.
 2. Machine according to claim 1, characterized in that said longitudinal welding bar is movable in either sense also in the longitudinal direction with respect to the tubular forming element and said movable transverse welding and cutting units are fixed to guiding and driving elements which allow said units to follow cyclical closed-loop paths.
 3. Machine according to claim 1, characterized in that said movable welding bar follows a cyclical closed-loop path comprising: a first longitudinal welding movement in the direction of travel of the film where it is located at a minimum distance from the tubular forming element; a second transverse movement away from the tubular forming element; a third longitudinal return movement in the opposite direction to the direction of the first longitudinal movement; and a final transverse movement towards the tubular forming element.
 4. Machine according to claim 1, characterized in that said movable longitudinal welding bar comprises reaction means positioned inside the tubular forming element and movable longitudinally together with said movable bar, said tubular forming element being provided with a longitudinal groove designed to allow cooperation of said movable bar with the associated reaction means.
 5. Machine according to claim 4, characterized in that said reaction means comprise a reaction bar positioned inside a closed longitudinal groove formed along the tubular forming element, said reaction bar being positioned flush with the outer surface of said tubular forming element so that the superimposed strips of film to be welded longitudinally are positioned between it and the longitudinal welding bar.
 6. Machine according to claim 4, characterized in that said reaction means comprise a tubular member located coaxially inside the tubular forming element, said tubular forming element being provided with a longitudinal groove which allows cooperation between said movable longitudinal welding bar and said tubular reaction member.
 7. Machine according to claim 1, characterized in that said movable longitudinal welding bar is connected, by means of an associated movable frame, to an actuating slide sliding along a longitudinal guide fixed to a support structure, said slide being displaced by means of suitable operating means.
 8. (canceled)
 9. Machine according to claim 1, characterized in that said tubular forming element comprises upstream a forming collar provided with a rear inclined surface, two front surfaces inclined in the opposite direction to said rear surface and at least two elements for superimposing the two strips of the plastic film wrapped around said front surfaces, said superimposing elements being suitably spaced from each other.
 10. (canceled)
 11. Machine according to claim 1, characterized in that said means for feeding the film along the tubular forming element comprise at least one pair of belts in contact with the tubular forming element and therefore with the film in two diametrically opposite positions and provided with suitable conveying rollers.
 12. (canceled)
 13. Machine according to claim 1, characterized in that said elements for guiding and driving the movable transverse welding and cutting units form on the sides of the film leaving the tubular forming element two closed and identical annular paths along each of which at least two of said movable units are constrained in diametrically opposite positions, so that each welding unit situated on one side of the film is coupled, along a straight, working, welding section of said annular path, with a corresponding welding unit situated on the other side of the film.
 14. Machine according to claim 13, characterized in that each of said annular paths formed by said guiding and driving elements comprises a first straight, working, welding section, a first arc-like connecting section, a second straight return section and a second arc-like connecting section.
 15. Machine according to claim 13, characterized in that each of said annular paths formed by said guiding and driving elements has a triangular shape and comprises three straight sections on each of which a movable unit for transversely welding and cutting the film is positioned.
 16. Machine according to claim 13, characterized in that each of said welding units comprises on one side welding teeth and cutting means, said welding teeth being fastened by means of rotational pins to a support element fastened to at least one pair of chains or belts for driving said welding units along said closed-loop path. 17.-19. (canceled)
 20. Machine according to claim 16, characterized in that each movable welding and cutting unit comprises, between said welding teeth, centring means for allowing correct alignment and relative positioning of a first movable unit provided along an annular path and situated on one side of the film with an associated second movable unit situated along the other annular path positioned on the other side of the film.
 21. Machine according to claim 20, characterized in that said centring means comprise a nose formed on a first movable unit between said welding teeth and a corresponding notch formed on a second movable unit which, during transverse welding and cutting of the film, must be coupled with said first movable unit.
 22. Machine according to claim 16, characterized in that the elements supporting the movable welding units are connected to a support plate to which an arm is fastened, said arm having, fixed thereto, a plurality of contacts making sliding contact along electrified tracks which follow the path of said drive chains or belts of the movable units.
 23. Machine according to claim 1, characterized in that each of the movable welding units comprises a pair of rollers travelling along a cam track guiding said movable units during their annular movement along said closed-loop paths.
 24. (canceled)
 25. Machine according to claim 1, characterized in that each of said movable transverse welding units comprises metal heads designed to slide along the associated metal annular tracks in order to detect the operating temperature of said movable units.
 26. Machine according to claim 1, characterized in that each of said movable transverse welding and cutting units comprises a box-shaped body having, positioned inside it, at least one blade or a counter-blade movable transversely in either sense for transversely cutting the film.
 27. Machine according to claim 26, characterized in that said blade or counter-blade is connected to a head which is displaceable transversely and which carries rollers travelling along a cam track controlling said blade or said counter-blade, said head being connected to said blade or to said counter-blade by means of a tubular element which passes through said support plate.
 28. (canceled)
 29. Machine according to claim 2, characterized in that it comprises members for folding the bottom of the packages, positioned upstream of the said movable transverse welding and cutting units on two diametrically opposite sides of the film in tubular form, each of said folding members being connected to at least one pair of longitudinal arms able to pivot so as to move towards or away from said film, and therefore the tubular forming element, via suitable guiding and operating means. 30.-33. (canceled)
 34. Machine according to claim 11, characterized in that at least one of said rollers of one of said belts feeding the film is fixed to a shaft connected to a motor for operating and acting as a counterweight for said belts, each of said belts being supported by a plate pivoting relative to a structure in turn pivoting and hinged on a fixed structure.
 35. Machine according to claim 34, characterized in that said shaft, intended for at least one roller of at least one of said belts and operated by said motor, has, keyed thereon, a toothed wheel around which there is wound a belt or chain for transmitting the movement to a second toothed wheel keyed onto a second shaft provided on at least one roller of the other belt feeding the film.
 36. Machine according to claim 23, characterized in that said cam tracks guiding the movable transverse welding and cutting units comprise working welding sections which are interchangeable and have active transverse welding sections of different lengths.
 37. Machine according to claim 1, characterized in that it comprises two units for transversely welding and cutting the film which are arranged opposite each other and are designed to weld and cut said film at the same moment the bar located upstream performs the longitudinal weld.
 38. Machine according to claim 1, characterized in that it comprises pairs of movable means for clamping in position the film to be welded, said means being provided with a least one opening for receiving the transverse welding heads and the elements for transversely cutting the film.
 39. Machine according to claim 38, characterized in that said movable means for clamping the film in position are supported by means of the plates designed to travel along closed-loop tracks, movable means for driving said plates being provided along the said tracks.
 40. Machine according to claim 39, characterized in that it comprises a support structure, on each side wall of which two closed-loop and symmetrically arranged tracks are positioned, at least one of said plates supporting the means for clamping the film in position travelling along each section of said tracks.
 41. Machine according to claim 1, characterized in that it comprises, upstream of the tubular forming element, a dispenser for dispensing loose material, having at least one pair of chambers designed to supply alternately said tubular forming element with said loose material.
 42. Machine according to claim 1, characterized in that it comprises movable baffles designed to be introduced or extracted, along the sides of the channel through which the loose material passes, into/from the tubular forming element so as to form steps able to limit the falling height of the loose material inside said through-channel. 